Apparatus and method for installing casing in a borehole

ABSTRACT

An apparatus and method of installing a casing string in a borehole, the apparatus comprising a propulsion system movable through the borehole; the propulsion system having an attachment member; and the attachment member being engagable with the casing string causing the casing string to move with the propulsion system through the borehole. The apparatus further including a conduit for circulating fluids through the propulsion system to provide the power to move the propulsion system. The propulsion system may also be disposable.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 10/262,136, filed Oct. 1, 2002 and entitledApparatus and Methods for Installing Casing in a Borehole, thisapplication being hereby incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

The embodiments relate generally to methods and apparatus for movementof equipment in passages. More particularly, the embodiments relate to apropulsion system for pulling casing into boreholes.

The art of drilling vertical, inclined, and horizontal boreholes playsan important role in the oil and gas industry. For example, a typicaloil or gas well comprises a vertical borehole that is drilled by arotary drill bit attached to the end of a drill string. The drill stringis typically constructed of a series of connected links of drill pipethat extend between surface equipment and the drill bit. A drillingfluid, such as drilling mud, is pumped from the surface through theinterior surface or flow channel of the drill string to the drill bit.The drilling fluid is used to cool and lubricate the drill bit, andremove debris and rock chips from the borehole created by the drillingprocess. The drilling fluid returns to the surface, carrying thecuttings and debris, through the space between the outer surface of thedrill pipe and the inner surface of the borehole.

Conventional drilling often requires drilling numerous boreholes torecover hydrocarbons, such as gas and oil, or mineral deposits. Forexample, drilling for oil and gas usually includes drilling a verticalborehole until the reservoir is reached. The hydrocarbons are thenpumped from the reservoir to the surface. As known in the industry,often a large number of vertical boreholes must be drilled within asmall area to recover the hydrocarbons within the reservoir. Thisrequires a large investment of resources and equipment and is veryexpensive. Additionally, the hydrocarbons within the reservoir may bedifficult to recover for several reasons. For instance, the size andshape of the formation, the depth at which the hydrocarbons are located,and the location of the reservoir may make exploitation of the reservoirvery difficult. Further, drilling for oil and gas located under bodiesof water, such as the North Sea, often presents greater difficulties.

In order to recover hydrocarbons from these difficult to exploitreservoirs, it may be desirable to drill a borehole that is notvertically orientated. For example, the borehole may be initiallydrilled vertically downwardly to a predetermined depth and then drilledat an inclination to vertical to the desired target location. In othersituations, it may be desirable to drill an inclined or horizontalborehole beginning at a selected depth. This allows the hydrocarbonslocated in difficult-to-reach locations to be recovered.

While several methods of drilling are known in the art, two frequentlyused methods to drill vertical, inclined, and horizontal boreholes aregenerally known as rotary drilling and coiled tubing drilling. In rotarydrilling, a drill string, consisting of a series of connected segmentsof drill pipe, is lowered from the surface using surface equipment suchas a derrick and draw works. Attached to the lower end of the drillstring is a bottom hole assembly (“BHA”). The BHA typically includes adrill bit and may include other equipment known in the art such as drillcollars, stabilizers, and heavy-weight pipe. The other end of the drillstring is connected to a rotary table or top drive system located at thesurface. The top drive system rotates the drill string, the BHA, and thedrill bit, allowing the rotating drill bit to penetrate into theformation. The direction of the rotary drilled borehole can be graduallyaltered by using known equipment such as a downhole motor with anadjustable bent housing to create inclined and horizontal boreholes.

Another type of known drilling is coiled tubing drilling. In coiledtubing drilling, the drill string tubing is fed into the borehole by aninjector assembly. In contrast to rotary drilling, the drill string isnot rotated. Instead, a downhole motor as part of the BHA providesrotation to the drill bit. Because the coiled tubing is not rotated orused to force the drill bit into the formation, the strength andstiffness of the coiled tubing is typically much less than that of thedrill pipe used in comparable rotary drilling. Thus, the thickness ofthe coiled tubing is generally less than the drill pipe thickness usedin rotary drilling, and the coiled tubing generally cannot withstand thesame rotational and tension forces in comparison to the drill pipe usedin rotary drilling.

The use of coiled tubing drilling typically eliminates the use ofconventional rigs and conventional drilling equipment. See, for example,U.S. Pat. Nos. 5,215,151; 5,394,951 and 5,713,422, all herebyincorporated herein by reference. The BHA may also include a propulsionsystem that propels the bit down the borehole. One such propulsionsystem is a thruster that pushes off the lower terminal end of thecoiled tubing and does not rely upon contacting or gripping the insidewall of the borehole.

Another such self-propelled propulsion system is manufactured by WesternWell Tool. The propulsion system includes an upper and lower housingwith a packerfoot mounted on each end. Each housing has a hydrauliccylinder and ram for moving the propulsion system within the borehole.The propulsion system operates by the lower packerfoot expanding intoengagement with the wall of the borehole with the ram in the lowerhousing extending in the cylinder to force the bit downhole.Simultaneously, the upper packerfoot contracts and moves to the otherend of the upper housing. Once the ram in the lower housing completesits stroke, then the hydraulic ram in the upper housing is actuated topropel the bit and motor further downhole as the lower packerfootcontracts and resets at the other end of the lower housing. This cycleis repeated to continuously move the BHA within the borehole. Thepropulsion system can propel the BHA in either direction in theborehole. Flow passages are provided between the packerfeet and housingsto allow the passage of drilling fluids through the annulus formed bythe coiled tubing and borehole.

Various companies manufacture other types of self-propelled propulsionsystems for propelling the bit and pulling steel coiled tubing in thewell. These propulsion systems include self-propelled wheels thatfrictionally engage the wall of the borehole. However, there is verylittle clearance between the wheels of the propulsion system and thewall of the borehole and problems arise when the wheels encounter ridgesor other variances in the dimensions of the wall of the borehole.Further, at times there is an inadequate frictional engagement betweenthe wheels and the wall of the borehole to adequately propel thepropulsion system.

Other companies also offer propulsion systems to “walk” the end of awireline down a cased borehole. However, these propulsion systems engagethe interior wall of a casing having a known inside dimension. One suchpropulsion system is manufactured by Schlumberger.

Another form of drilling is composite tubing drilling. Similar to coiledtubing drilling, a propulsion system can also be used with compositetubing to drill a borehole. An example of a drilling system using apropulsion system with composite coiled tubing is U.S. Pat. No.6,296,066, hereby incorporated herein by reference. With compositetubing drilling, instead of using coiled metal tubing, composite coiledtubing is used as the drilling conduit for transfer of the drillingfluids. With composite tubing, the drill string is also not rotated.

For all of the methods of drilling discussed above, during the course ofthe drilling program, the borehole typically has one or more “casingstrings” run and cemented in place. A typical drilling program firstinvolves drilling a large diameter borehole from the earth's surface forseveral thousand feet. A “surface casing” string is then run into theborehole and cemented in place. After the cement in the annulus hascured or hardened, another drill bit is utilized to drill through thecement in the surface casing to drill a second and deeper borehole intothe earth formations. Typically, the subsequent drill bit has a smallerdiameter that the initial drill bit such that the second borehole has asmaller diameter than the diameter of the surface borehole. However, itshould be appreciated that bi-center bits and wing reamers may be usedto enlarge the diameter of the second borehole.

With respect to the section of borehole subsequently drilled below asurface casing; at an appropriate depth, the drilling of the borehole isdiscontinued and a string of pipe commonly called a casing or liner isinserted through the surface casing. As a matter of nomenclature, aliner is a string of pipe typically suspended in the lower end of thepreviously set casing by a liner hanger so that the lower end of theliner does not touch the bottom of the borehole and the liner thus issuspended under the tension of the pipe weight on the liner hanger. Insome instances, a liner is set on the bottom of the borehole but itsupper end does not extend to the earth's surface.

If the pipe set in the borehole subsequently drilled extends to thesurface of the earth it is also called a casing. When the cementingoperation is completed and the cement sets, there is a column of cementin the annulus of the subsequent string of pipe. The casing strings areusually comprised of a number of joints, each being on the order offorty feet long, connected to one another by threaded connections orother connection means. Also, the joints are typical metal pipes, butmay also be non-meal materials such as composite tubing.

Typically, the casing string is merely gravity fed into a verticalborehole. If a top drive rig is used, the rig can hydraulically forcethe casing string down into the borehole. If gravity fed, however, theweight of the casing is used to install the casing in the borehole.Typically, a casing shoe is disposed on the lower end of the casingstring to close off the lower end of the casing string. The casing shoecloses off the lower end of the string so that the casing then serves asa pressure vessel in which fluid pressure can be applied to help forcethe casing down hole. The shoe typically is bullet shaped with aspherical-type face. A float valve may be attached to the lower end ofthe casing that allows the fluid to pass down the casing and out throughthe lower end to allow fluid circulation.

The advent in recent years of highly deviated or horizontal wells in theoil and gas industry has increased both the frequency and seriousness ofdifficulties encountered while running borehole casing strings.Particularly, problems occur in a borehole that has an extended reachhorizontal portion. Horizontal wells may be at shallow depths where thevertical portion of the well is small. With a small vertical portion,the vertical length of the casing is short whereby minimum weight isprovided by the drill string to allow gravity to assist in setting thecasing. In addition, in a horizontal well, the drag becomes so great onthe casing string that it can no longer be forced into the borehole.Also, if a borehole has high build rates, such as 30° per hundred feetplus, there can be a wash out in the curved section. If there is a washout, the end of the pipe may tend to bury itself into the wash outportion rather than follow the bends or curves in the borehole. Thus,the end of the pipe could dead end into one of the cavities caused bythe wash out rather than make the turn in the borehole.

Another prior art solution to these problems includes floating the pipeby making the string of casing a closed vessel and either filling thecasing with a low density fluid or possibly only having air in thecasing. The borehole is filled with fluid to place a column on the wellto maintain control. The fluid inside the casing has a lower densitythan the fluid forming the column in the annulus and causes the casingstring to tend to be buoyant and “float” in the borehole fluid. Causingthe casing string to float reduces the drag on the highly deviatedborehole wall. This methodology, however, is delicate because of thecollapse pressure of the casing. The casing will collapse if thepressure differential across the casing wall becomes too great. In anyevent, floating the casing still does not completely eliminate the dragon the casing and thus the methodology is still subject to the problemsdiscussed above for non-floating casing.

The consequence of encountering such difficulties are, at best, delaysin the schedule of the well program and, at worst, having to drill allor part of the well again. In any case, significant additional cost isinvolved. Thus, there exists a need for an apparatus and method ofinstalling casing into highly-deviated and horizontal boreholes. Thecasing must thus be able to maneuver through curves in the borehole. Thecasing must also be able to be installed in boreholes of great length,in the order of 50,000 feet. The apparatus and method of installing thecasing must also cost-effectively install casing into the borehole. Thecost-effectiveness not only takes into consideration the resourcesneeded to install the casing, but also the amount of time required.

Other objects and advantages of the invention will appear from thefollowing description.

SUMMARY OF THE PREFERRED EMBODIMENTS

The preferred embodiments provide an improved method and apparatus formovement of equipment in passages. Specifically, the embodiments provideimproved methods and apparatus for moving casing within a borehole.

One preferred embodiment includes an apparatus and method for movingcasing into a borehole using a propulsion system. The propulsion systemincludes a housing having an upstream section with a traction module anda downstream section with a traction module. The traction modules areeach connected to a ram mounted in a cylinder within one of the housingsections for propelling the housing up and down the borehole. Inoperation, one of the traction modules expands to engage the boreholewall ID, whether it be a cased or open borehole, while the hydraulic ramforces the housing downhole as the other traction module moves to theother end of its housing section in preparation for actuating its ram tomove the housing farther downhole.

The propulsion system is not only capable of movement within the innerdiameter (“ID”) of the casing string, but also operates within of theinner diameter of the open borehole. Extending from the uphole end ofthe propulsion system is a power fluid coiled tubing. This tubing allowsfluid-flow from a surface power fluid supply that powers the propulsionsystem as it travels downhole. The power fluid returns to the surfacethrough the annulus formed by the casing string and cased or openborehole wall.

The upstream end of the propulsion system includes an annular shoulderprojecting radially from the outside of the propulsion system. Thelower, or downhole, terminal end of the casing string to be engaged bythe propulsion system includes a corresponding annular collar extendingradially inward on the ID of the casing. The outer diameter (“OD”) ofthe propulsion system shoulder is greater than the ID of the casingcollar such that the housing of the propulsion system can pass throughthe casing collar, but the propulsion system shoulder cannot. In otherwords, the propulsion system shoulder engages the casing collar andbears against the casing collar to pull the casing string downhole.

To install the casing string, the casing string is first inserted intothe borehole as far as possible using conventional methods such asgravity feeding or “floating”. Once the casing string cannot proceedfurther downhole, the propulsion system is inserted into the uphole endof the casing string at the surface with the power fluid coiled tubingattached. The propulsion system travels through the casing string untilthe propulsion system reaches the downhole end of the casing string. Asthe propulsion system reaches the end of the casing string, thepropulsion system housing passes through the casing collar until thepropulsion system shoulder on the rear of the propulsion system engagesthe casing collar on the end of the casing string. After the shoulderengages the collar, as the propulsion system travels further downhole,it pulls the casing string down through the borehole until the downholeend of the casing reaches the desired depth. The propulsion system isthen retrieved either by reversing the propulsion system to travel backthrough the casing string to the surface or by rewinding the power fluidcoiled tubing onto a powered tubing spool.

In another preferred embodiment, the casing string is used to supply thepower fluid to the propulsion system so as to avoid the need for a powerfluid coiled tubing. Further, a disposable propulsion system would beused whereby the propulsion system would be left downhole once theborehole has been completely drilled and the casing string installed. Itshould be appreciated that the propulsion system would be madeinexpensively since it would not be retrieved. The engagement betweenthe casing collar and propulsion system shoulder would provide anadequate seal so as to direct the power fluid through the propulsionsystem and drive the system. The pressure of the power fluid against thepropulsion system shoulder assists in the sealing engagement. Thispreferred embodiment otherwise operates similarly to the first preferredembodiment and saves the cost of a power fluid coiled tubing and thetime required to retrieve the propulsion system from the borehole.

Various methods may be used to add a new section of casing to the casingstring once the casing string travels far enough to add another sectionof casing to the casing string at the surface. One method includesdisconnecting the power fluid coiled tubing from the fluid pump eachtime a new casing section is to be added. After the power fluid coiledtubing is disconnected, it is fed through the downhole end of the nextlength of casing. The casing section is then attached to the uphole endof the casing in the borehole. The power fluid coiled tubing is thenre-connected to the fluid pump and the installation process isre-commenced. Another method includes threading the power fluid coiledtubing through multiple casing sections to later be added to the casingstring. As new casing sections are required, the next casing sectionthreaded onto the power fluid coiled tubing is attached to the casingstring. If all of the threaded casing sections have been added to thecasing string, then the power fluid coiled tubing is disconnected tothread additional casing sections. Still another method includesremoving the propulsion system from the borehole to the surface eachtime it is necessary to add a new casing section and then re-insertingthe propulsion system into the casing string to travel back downhole tocontinue pulling the casing string into the borehole. It should beappreciated that other methods may be used to add new casing sections.

New casing sections are added until the casing string reaches the bottomof the newly drilled borehole. Once the casing is installed in theborehole, the propulsion system is then retrieved back uphole, throughthe casing string to the surface where it is removed from the casingstring.

Still another preferred embodiment includes installing multiple casingstrings into a newly drilled borehole. This embodiment is particularlyadvantageous when the horizontal portion of the borehole is very longand the propulsion system cannot install the entire length of the casingstring in the new borehole. In this embodiment multiple lengths ofcasing string are installed such as for example a first casing lengthand a second casing length. The second casing length would have asmaller diameter than the first length so that the second casing lengthwould pass through the first casing length.

The first casing length includes a downhole connection on its lowerterminal end which also serves as a casing collar. The second casinglength, in addition to the casing collar described above, also includesa snap collar or other similar uphole connection on the upstream end ofthe second casing length. The propulsion system shoulder bears againstthe casing collar on the lower end of the first casing length to pullthe first casing length downhole. After the first casing length hasreached the desired depth, the propulsion system is then pulled out ofthe borehole.

The second casing length is then run into the borehole using thepropulsion system. The propulsion system shoulder bears on the casingcollar on the lower end of the second casing length. The propulsionsystem pulls the second casing length through the first casing lengthuntil the second casing length reaches its desired depth and the upholeconnection on the second casing length stab-connects with the downholeconnection on the downstream end of the first casing length, thusconnecting the first casing length with the second casing length. Thepropulsion system is then retrieved from the borehole and an additionalcasing length installed as necessary. This process is repeated until theentire horizontal borehole is lined with a length of casing. Thus, thecasing string is run in lengths until the all the casing has beeninstalled.

Thus, the preferred and alternative embodiments comprise a combinationof features and advantages that enable them to overcome various problemsof prior devices. The various characteristics described above, as wellas other features, will be readily apparent to those skilled in the artupon reading the following detailed description of the preferred andalternative embodiments, and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the preferred and alternativeembodiments, reference will now be made to the accompanying drawings,wherein:

FIG. 1 is a schematic view of a conventional land well casingarchitecture;

FIG. 2 is a schematic view of one preferred embodiment of a propulsionsystem engaged with an end of a casing string;

FIG. 3 is a cross-sectional view of the propulsion system of FIG. 2;

FIG. 4 is a cross-sectional view taken at plane 4-4 in FIG. 3 showingone of the traction modules;

FIG. 5 is a schematic view of another preferred embodiment of thepropulsion system using the casing string as the means for providingpower fluid to the propulsion system; and

FIG. 6 is a schematic view of a still another preferred embodiment of apropulsion system engaged with an end of a casing length that is to bejoined with the a previously installed casing length.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While preferred embodiments of this invention are shown and described,modifications thereof can be made by one skilled in the art withoutdeparting from the spirit or teaching of this invention. The embodimentsdescribed herein are exemplary only and are not limiting. Manyvariations and modifications of the apparatus and methods are possibleand are within the scope of the invention. Accordingly, the scope ofprotection is not limited to the embodiments described herein, but isonly limited by the claims that follow, the scope of which shall includeall equivalents of the subject matter of the claims.

In the description that follows, like parts are marked throughout thespecification and drawings with the same reference numerals,respectively. The drawing figures are not necessarily to scale. Certainfeatures may be shown in exaggerated in scale or in somewhat schematicform and some details of conventional elements may not be shown in theinterest of clarity and conciseness. For example, standard fluid sealingtechniques, such as the use of annular O-ring seals, and threadedconnections may be depicted but not described in detail herein, as suchtechniques are well known in the art. As such, construction details arenot important to operation of the embodiments, and are well understoodby those of skill in the art, they will not be discussed here. In usingthe terms “above”, “up”, “upward”, “uphole” or “upper” with respect to amember in the well bore, such member is considered to be at a shorterdistance from the surface through the bore hole than another memberwhich is described as being “below”, “down”, “downward”, “downhole”, or“lower”. It should also be appreciated that the use of the term “casing”throughout this application also includes liners or any other form oftubular member.

Referring initially to FIG. 1, a typical well 100 is shown. The well 100includes sections of structural casing 102 extending into concentricboreholes 104 with each of the structural casing 102 having decreasingdiameters. The sections of structural casing 102 extend to varyingdepths according to the design of the well 100 and particularly to thedifferent formations through which the boreholes extend. Once thestructural casing 102 is in place, a further borehole 106 is drilled tothe reservoir 108.

Directional drilling methods known in the art allow the well to bedrilled in a deviated direction from vertical to deviated. This type ofwell is referred to as a “deviated” borehole. In addition, the boreholecan deviate from vertical to such an extent as to run horizontally forsome distance. This type of borehole is referred to as a “horizontal”borehole. It should also be appreciated that a borehole can have morethan one deviation, or curve, and can thus comprise any number shapes asit travels into the earth. The well 100 includes a borehole 14 having avertical portion 110 and a deviated portion 112 with the deviatedportion 112 having a horizontal portion 114. A completions casing 12 isinstalled that extends from the surface 116 to the reservoir 108. Thecompletions casing 12 forms an annulus 40 with the wall of the borehole.

Referring now to FIG. 2, one preferred embodiment includes an apparatus10 for installing casing 12 within borehole 14. The apparatus 10includes a propulsion system 16 having one end, such as uphole end 17,attached to the lower end of a power fluid coiled tubing 26. The upperend of the power fluid coiled tubing 26 is attached to a power fluidpump (not shown) at the surface 116. Power fluid coiled tubing 26 may bemetal coiled tubing or preferably composite coiled tubing 26. Powerfluid coiled tubing 26 allows fluid-flow from the surface 116 to thepropulsion system 16 that powers the propulsion system 16 as it travelswithin borehole 14. Propulsion system 16 includes a housing 20 with aflow bore 22 therethrough for the fluids flowing down through theflowbore 24 of power fluid coiled tubing 26 extending from the upholeend 17 of the propulsion system 16. The propulsion system 16 engages thecompletion casing 12, as hereinafter decried, for propelling the casing12 downhole.

Referring now to FIGS. 3 and 4, there is shown a schematic of a typicalpropulsion system 16. For self-propulsion, propulsion system 16 becomesthe prime mover and includes a downstream packer-like traction module 28and an upstream packer-like traction module 30. It should be appreciatedthat the propulsion system 16 may include more than two tractionmodules. Housing 20 of propulsion system 16 includes a downstreamsection 32 and an upstream section 34.

As best shown in FIG. 4, there is shown a cross-section of tractionmodule 30. Because the traction modules 28, 30 are similar inconstruction, a description of one traction module approximates thedescription of the other. Traction module 30 includes steel feet 36around its outer circumference that may be expanded and contracted intoengagement with the wall 15 of borehole 14. A plurality of flutes orlongitudinal fluid flow passages 38 are provided around the innercircumference of the steel bands forming feet 36 to allow fluid to flowupstream through annulus 40 when traction module 30 is expanded intoengagement with the wall 15 of borehole 14. The traction modules 28, 30may have independently inflatable, individual chambers, as hereinafterdescribed in detail, for expanding modules 28, 30 eccentrically withrespect to the housing 20.

Downstream housing section 32 includes a tubular cylinder 42 in which isdisposed a hydraulic ram 44 on which is mounted downstream tractionmodule 28. Hydraulic ports 46, 48 are disposed at the opposite ends oftubular cylinder 42 for applying hydraulic pressure to ram 44. Hydraulicports 50, 52 are disposed adjacent downstream traction module 28 forexpanding and contracting the traction module in and out of engagementwith the wall of borehole 12. It should be appreciated that upstreamhousing section 20 is similar in construction and operation withcylinder 43, ram 45, and ports 47, 49, 51, and 53. It should also beappreciated that propulsion system 16 includes a series of valves usingfluid pressure for the actuation of rams 44, 45 and traction modules 28,30 mounted on rams 44, 45, respectively.

The cycle of propulsion system 16 includes expanding downstream tractionmodule 28 into engagement with the interior wall 15 of borehole 14 withthe upstream traction module 30 in the contracted and non-engagedposition as shown in FIG. 3. Hydraulic pressure is applied throughhydraulic ports 48, thus applying pressure to ram 44. As pressure isapplied against ram 44, which is stationary relative to the borehole 14due to its attachment to engaged traction module 28, housing 20 movesdownhole. Hydraulic fluid is simultaneously applied through hydraulicport 49 causing contracted upstream traction module 30 to move forwardon upstream housing section 34. Upstream traction module 30 thus movesforward simultaneously with housing 20 moving downhole. Once thedownstream traction module 28 reaches the upstream end of tubularcylinder 42, it has completed its forward stroke and is contracted.Simultaneously, upstream traction module 30 has now completed its travelto the downstream end of tubular cylinder 43 and it is in its resetposition to start its downward stroke. Traction module 30 is thenexpanded into engagement with borehole 14. As hydraulic pressure isapplied through hydraulic port 47 and against upstream ram 45,propulsion system 16 strokes downwardly. Simultaneously, downstreamtraction module 28 is contracted and reset by applying hydraulicpressure through upstream port 46. The cycle is then repeated allowingthe propulsion system 16 to move continuously downstream in one fluidmotion. Each stroke approximates the length of housing sections 32, 34.It should be appreciated that the propulsion system 16 is not onlycapable of movement within the borehole 14, but also is capable ofoperating within the ID of the structural casing 12 or any other casingalready in place in the borehole 14. The propulsion system 16 has thisability due to the expansion and contraction of the traction modules 28,30.

It should be appreciated that the hydraulic actuation may be reversedwhereby propulsion system 16 may be moved upstream in borehole 14. Inother words, propulsion system 16 can “walk” either forward, downstream,or backward, upstream in borehole 14. It also should be appreciated thatalthough propulsion system 16 is shown as being hydraulically actuated,it may also be operated electrically with power being provided throughpower transmission conductors.

It should also be appreciated that although the propulsion system 16 hasbeen described with two traction modules, the propulsion system 16 maybe configured with additional traction modules, such as three tractionmodules, depending upon the application.

Western Well Tool, Inc. manufactures a preferred propulsion systemhaving expandable and contractible upstream and downstream tractionmodules mounted on a hydraulic ram and cylinder for self-propellingdrilling bits. The Western Well Tool propulsion system is described in aEuropean Patent Application PCT/US96/13573 filed Aug. 22, 1996 andpublished Mar. 6, 1997, Publication No. WO 97/08418, hereby incorporatedherein by reference.

Other propulsion systems may be adapted for use with the preferredembodiment. Other types of propulsion systems include an inchworm byCamco International, Inc., U.S. Pat. No. 5,394,951, hereby incorporatedherein by reference and by Honda, U.S. Pat. No. 5,662,020, herebyincorporated herein by reference. See also U.S. Pat. No. 3,799,277,hereby incorporated herein by reference. Also, robotic propulsionsystems are produced by Martin Marietta Energy Systems, Inc. and aredisclosed in U.S. Pat. Nos. 5,497,707 and 5,601,025, each herebyincorporated herein by reference. Another company manufactures apropulsion system that it calls a “Helix”. See also “InchwormMobility—Stable, Reliable and Inexpensive,” by Alexander Ferwom andDeborah Stacey; “Oil Well Tractor” by CSIRO-UTS of Australia; “WellTractor for Use in Deviated and Horizontal Wells” by Fredrik Schussler;“Extending the Reach of Coiled Tubing Drilling (Thrusters, Equalizers,and Tractors)” by L. J. Leising, E. C. Onyia, S. C. Townsend, P. R.Paslay and D. A. Stein, SPE Paper 37656, 1997, all hereby incorporatedherein by reference. See also “Well Tractors for Highly Deviated andHorizontal Wells”, SPE Paper 28871 presented at the 1994 SPE EuropeanPetroleum Conference, London, Oct. 25-27, 1994, hereby incorporatedherein by reference.

Referring again to FIG. 2, the upstream end 17 of the propulsion system16 includes an attachment member for attaching the propulsion system 16to the casing 12. In one preferred embodiment, the propulsion systemattachment member is an annular shoulder 54 extending radially outwardfrom the outside of uphole end 17 of housing 20 of the propulsion system16. The lower, or downhole, end of casing 12 also includes an attachmentmember. In one preferred embodiment, the casing attachment member is anannular collar 56 on the ID of the casing 12. The annular collar 56 hasa inner diameter greater than the outer diameter of housing 20 such thatlousing 20 will pass through the annular collar 56. The OD of thepropulsion system shoulder 54 is greater than the ID of the casingcollar 56 such that the housing 20 of propulsion system 16 can passthrough the casing collar 56, but the propulsion system shoulder 54cannot such that propulsion system shoulder 54 bears against casingannular collar 56.

It should be appreciated that casing annular collar 56 may be affixed tothe end of casing 12 in various manners. In one embodiment, annularcollar 56 is part of a sub 57 threaded onto the lowermost section ofcasing 12 making up the casing string. Annular collar 56 must be strongenough to withstand the forces to be applied to it by propulsion system16 to pull the casing string into the borehole 14.

It should be appreciated that the annular shoulder 54 on propulsionsystem 16 may be removable from housing 20. For example, annularshoulder 54 may be threaded onto housing 20. Another example includesmounting the annular showered 54 on the connection between the powerfluid coiled tubing 26 and housing 20 of the propulsion system 16. Thiswill allow annular shoulders 54 with different outside diameters to bemounted on propulsions system 16 to accommodate the size of the casing12 being installed.

In accordance with the preferred methods of operation, the casing string12 is first installed into the borehole 14 as far as possible usingconventional methods such as gravity feeding or “floating”. Once thecasing string 12 cannot proceed further downhole, the propulsion system16 is inserted into the uphole end of the casing string 12 at thesurface 116 with the power fluid coiled tubing 26 attached. Thepropulsion system 16 travels through the interior of the casing string12 until the propulsion system 16 reaches the downhole end 18 of thecasing string 12. As the propulsion system 16 reaches the end 18 of thecasing string 12, the propulsion system housing 20 passes through the IDof casing collar 56 until the propulsion system shoulder 54 engages thecasing collar 56. After the shoulder 54 engages the collar 56, as thepropulsion system 16 travels further downhole, it pulls the casingstring 12 further down through the borehole 14. This is particularlyadvantageous in installing the casing string 12 in a highly deviatedborehole 112 and most advantageous in a horizontal portion 114 of theborehole 14.

The propulsion system 16 then travels further downhole, pulling thecasing string 12 down through the borehole 14 until the downhole end 18of the casing string 12 reaches the desired depth. The propulsion system16 is then retrieved either reversing the propulsion system 16 to travelback through the casing string 12 to the surface 116 or by rewinding thepower fluid coiled tubing 26 onto a powered tubing spool.

Referring now to FIG. 5, there is shown another preferred embodiment. Inthis embodiment, the casing string 12 is used to supply the power fluidto the propulsion system 16 so as to avoid the need for a power fluidcoiled tubing. Further, a disposable propulsion system would be usedwhereby the propulsion system 16 would be left downhole once theborehole 14 has been completely drilled and the casing string 12installed. It should be appreciated that the propulsion system 12 wouldbe made inexpensively because it would not be retrieved. The engagementat 55 between the casing collar 56 and propulsion system shoulder 54would provide an adequate seal so as to direct the power fluid 62through the propulsion system 16 and drive the system. The pressure ofthe power fluid 62 against the propulsion system shoulder 54 assists inthe sealing engagement at 55. This preferred embodiment otherwiseoperates similarly to the first preferred embodiment and saves the costof a power fluid coiled tubing and the time required to retrieve thepropulsion system from the borehole.

Once the casing string 12 travels far enough to add on more sections ofcasing, the propulsion system 16 stops, reverses, and then travels backuphole to the surface 108 where it is retrieved from the casing string12. As many sections of casing as can be handled on the surface 108 arethen added to the casing string 12. The propulsion system 16 is thenre-inserted into the casing string 12 and the process is repeated untilthe casing string 12 reaches the reservoir 106. Once the casing 12 isinstalled in the borehole 14, the propulsion system 16 then travelsuphole, back through the casing 12 to the surface 108 where it isretrieved from the casing string 12.

Various methods may be used to add a new section of casing to the casingstring 12 once the casing string 12 travels far enough to add anothersection of casing to the casing string 12 at the surface 116. One methodincludes disconnecting the power fluid coiled tubing 26 from the fluidpump each time a new casing section is to be added. After the powerfluid coiled tubing 26 is disconnected, it is fed through the downholeend of the next length of casing 12. The casing section is then attachedto the uphole end of the casing string 12 in the borehole 14. The powerfluid coiled tubing 26 is then re-connected to the fluid pump and theinstallation process is re-commenced.

Another method includes threading the power fluid coiled tubing 26through multiple casing sections to later be added to the casing string12. As new casing sections are required, the next casing section,threaded onto the power fluid coiled tubing 26, is attached to thecasing string 12. If all of the threaded casing sections have been addedto the casing string 12, then the power fluid coiled tubing 26 isdisconnected to thread additional casing sections.

Still another method includes removing the propulsion system 16 from theborehole 14 to the surface 116 each time it is necessary to add a newcasing section and then re-inserting the propulsion system 16 into thecasing string 12 to travel back downhole to continue pulling the casingstring 12 into the borehole 14. It should be appreciated that othermethods may be used to add new casing sections.

New casing sections are added until the casing string 12 reaches thebottom of the newly drilled borehole 14. Once the casing 12 is installedin the borehole 14, the propulsion system 16 is then retrieved backuphole, through the casing string 12 to the surface 116 where it isremoved from the casing string 12.

Referring now to FIG. 6, still another preferred embodiment includesinstalling multiple casing strings into a newly drilled borehole. Thisembodiment is particularly advantageous when the horizontal portion ofthe borehole is very long and the propulsion system cannot install theentire length of the casing string in the new borehole at one time. Inthis embodiment, multiple lengths, such as first casing length 58 andsecond casing length 60, of the casing string are installed. The secondcasing length 60 has a smaller diameter than the first length 58 so thatthe second casing length 60 can pass through the first casing length 58.

The first casing length 58 includes a downhole connection 64 on itslower terminal end 66, which also serves as a casing collar. The secondcasing length 60, in addition to the casing collar described above, alsoincludes a snap collar or other similar uphole connection 68 on theupstream end 70 of the second casing length 60.

In operation, initially the first casing length 58 is installed in theborehole 14 as previously described. The propulsion system shoulder 54bears against the casing collar connection 64 on the lower end 66 of thefirst casing length 58 to pull the first casing length 58 downhole.After the first casing length 58 has reached the desired depth, thepropulsion system 16 is then pulled out of the borehole 14.

The annular shoulder 54 on propulsion system 16 may be changed to anannular shoulder 54 which has a smaller outside diameter to accommodatethe smaller diameter second casing length 60. The second casing length60 is then run into the borehole 14 through the first casing length 58using the propulsion system 16. The propulsion system shoulder 54 bearson the casing collar 56 on the lower end of the second casing length 60.The propulsion system 16 pulls the second casing length 60 through thefirst casing length 58 until the second casing length 60 reaches itsdesired depth and the uphole connection 68 on the second casing length60 stab-connects with the downhole connection 64 on the downstream end66 of the first casing length 58, thus connecting the first casinglength 58 with the second casing length 60. The propulsion system 16 isthen retrieved from the borehole 18 and an additional casing length isinstalled as necessary. This process is repeated until the entirehorizontal borehole 114 is lined with a length of casing. Thus, thecasing string is run in lengths until the all the casing has beeninstalled.

While preferred embodiments of the invention have been shown anddescribed, modifications can be made by one skilled in the art withoutdeparting from the spirit of the invention.

1. An apparatus for installing casing in a borehole, the apparatuscomprising: a propulsion system movable through the borehole and atleast a portion of the casing; the propulsion system comprising anattachment member; and the attachment member being engageable with thecasing and causing the casing to move with the propulsion system throughthe borehole.
 2. The apparatus of claim 1 wherein the attachment memberincludes an extension projecting from the propulsion system.
 3. Theapparatus of claim 2 wherein the propulsion system extension projectsradially outward from the uphole end of the propulsion system.
 4. Theapparatus of claim 3 wherein the extension engages the casing causingthe casing to move with the propulsion system.
 5. The apparatus of claim1 further including a conduit for circulating fluids through thepropulsion system to provide the power to move the propulsion system. 6.The apparatus of claim 5 wherein the conduit is coiled tubing extendinginto the borehole comprising one end connected to the propulsion system.7. The apparatus of claim 1 wherein the propulsion system is disposable.8. An assembly for installing a casing string in a borehole, theapparatus comprising: a propulsion system movable through the boreholeand a portion of the casing string; the propulsion system comprising anattachment member; a casing section connected to the casing string andcomprising a connection member; and the attachment member beingengageable with the connection member and causing the casing string tomove with the propulsion system through the borehole.
 9. The assembly ofclaim 8 wherein the propulsion system is disposable.
 10. The assembly ofclaim 8 wherein the connection member projects radially inward from thecasing section and the attachment member projects radially outward ofthe propulsion system.
 11. The assembly of claim 10 wherein theconnection member is an annular collar and the attachment member is anannular shoulder, the annular collar comprising an inner diameter largeenough to allow the propulsion system to pass through but small enoughto prevent the annular shoulder from passing through.
 12. An assemblyfor installing casing in a borehole, the assembly comprising: apropulsion system movable through the borehole; the propulsion systemcomprising an attachment member; a casing string connected to thepropulsion system; and the casing string comprising a flowbore forcirculating fluids through the propulsion system to provide the power tomove the propulsion system.
 13. The assembly of claim 12 wherein thecasing string is sealed to the propulsion system.